Purified liquid sugar concentrate and method of manufacturing same

ABSTRACT

A PURE LIQUID SUGAR CONCENTRATE OF AT LEAST 65* BRIX IS PRODUCED DIRECTLY FROM A DILUTE SUGAR-CONTAINING LIQUID IN A REFINING PROCESS WHICH EXCLUDES CRYSTALLIZATION AS A REQUIRED PROCEDURE IN THE METHOD OF PURIFICATION. THE REFINING INCLUDES CONCENTRATION, DEMINERALIZATION IN A   MIXED RESIN ION EXCHANGE, FURTHER CONCENTRATION AND FILTRATION.

Feb 16, 1971 J ER ETAL 3,563,799

' PURIFIED LIQUID SUGAR CONCENTRATE AND METHOD OF MANUFACTURING SAMEFiled 001;. 2, 1967 I SUGAR-BEARING AGRICULTURAL PRODUCT JUICEEXTRACTION, CLAR/F/CAT/ON AIvD DEFECA T/ON TREA TMENT 3 il/LU TE sUGARcoIv TA/N/NG LIQU ID (ARRRox. IO BRIx) 5 EVAPORATOR W CONDENSED SUGARLIQUOR (30 GoBRIx) A URlF/ED LIQUID SUGAR CONCENTRATE(65-72BRIX) F/LERl0 I2 FINAL LIQUID PRODUCTJ BY 1% ,1, "QM

ATTYS United States Patent 3,563,799 PURIFIED LIQUID SUGAR CONCENTRATEAND METHOD OF MANUFACTURING SAME James F. Zievers and Clay W. Riley, LaGrange, and Charles J. Novotny, Hickory Hills, Ill., assignors toIndustrial Filter & Pump Mfg. Co., Cicero, Ill., a corporation ofIllinois Filed Oct. 2, 1967, Ser. No. 672,298 Int. Cl. C13d 3/14, 3/00;C13f 3/00 US. Cl. 127-46 2 Claims ABSTRACT OF THE DISCLOSURE A pureliquid sugar concentrate of at least 65 Brix is produced directly from adilute sugar-containing liquid in a refining process which excludescrystallization as a required procedure in the method of purification.The refining includes concentration, demineralization in a mixed resinion exchanger, further concentration and filtration.

SUMMARY OF THE INVENTION This invention relates to a process for thepurification of dilute sugar-containing liquids, such as sugar juice,obtained from any sugar-bearing agricultural plant. More particularly,it relates to a simplified process for manufacturing a purified liquidsugar concentrate containing at least 65 weight percent of sugar solidswhich process excludes the step of crystallization.

In the manufacture of refined sugar solutions it is conventionalpractice to purify or 'defecate raw sugar juice by first treating thesolutions with, for example, calcium hydroxide and carbon dioxide. Sugarsolutions which have been pre-treated in this manner are however, notsufficiently pure and therefore have to be subjected to further refiningor defecating treatment, particularly for the purpose of removingundesirable alkaline earth metal ions such as calcium and magnesium ionsand various colo r bodies.

The present invention is concerned with the further purification ofpre-treated dilute sugar solutions, i.e., sugar solutions or juiceswhich have been subjected to the customary lime-carbon dioxidedefecation treatment referred to or to similar equivalent pre-treatingprocedures.

Heretofore, pre-treated sugar solutions have been purified by removingthe ash components by chemical precipitation or by ion-exchange,followed by subsequent boiling and crystallization operations.Ion-exchange resins employed in sugar purification processes are thosehaving high de-ashing capacity, i.e., the ability to remove ionicimpurities and also having high refining capacity for aqueous solutions,i.e., the ability to remove organic impurities present in sugar liquorsfor example, color bodies and materials giving rise to color bodies,colloidal material and the like. As these desirable properties are notpossessed by any single exchanger system available it has been necessarytherefore to accept some compromise between quality of sugar liquoreflluent from the ion-exchangl systern and economical operation. Inorder to meet the problem, it has been necessary to utilizecrystallization as a separation procedure in order to manufacture asugar product of satisfactory purity from sugar solutions produced byconventional pretreating and ion-exchange methods. Crystallizationprocedures, however, are time consuming, require expensive equipment andare inherently inefficient from the point of view of percentage ofproduct recovered. Further, with the rising demand in industry forliquid sugar products, the requirement that the product to be sold as anaqueous solution be first separated in crystal form has become aparticularly burdensome problem. Yet so far as is known, no priorpractical process capable of industrial utilization has beenscccessfully employed in the manufacture of a purified liquid sugarconcentrate, which did not require crystallization as an essential stepin the purification of the final product.

Accordingly, among the objects of the present invention are to provide anovel purification method; to provide such a method which isparticularly adapted for the treatment of dilute sugar-containingsolutions; to provide such a method which can be utilized in thetreatment of sugar solutions obtained by the extraction of sugar bymeans of water from any sugar-bearing agricultural plant; and to providesuch a method by which a high purity juice or solution can be obtainedwith optimum efficiency which eliminates crystallization as an essentialstep of the process.

Briefly, the present invention provides a process for manufacturing apurified liquid sugar concentrate of at least 65 Brix directly from adilute sugar containing liquid which process excludes the step ofcrystallization. In accordance with the novel process a defecated dilutesugar-containing liquid is condensed to produce a sugar liquor of fromabout 30 to 60 Brix. The condensed sugar liquor is thereafterdecolorized and contacted with an ion-exchange material to removedissolved solids and organic impurities. Thereafter the ion-exchangetreated sugar liquor is further condensed to produce a liquid sugarproduct containing at least 65 weight percent of sugar solids.

Additional objects and advantages of the present invention will becomemore apparent from a consideration of the following specification andclaims, when taken in conjunction with the accompanying drawing,wherein:

The single figure illustrates diagrammatically an illustrative processembodying the present invention.

It is to be understood that there is no intention to limit the inventionto he specific forms and examples disclosed, but on the contrary, theinvention covers all modifications, alternatives, equivalents and usesfalling within the spirit and scope of the invention as expressed in theappended claims.

The dilute sugar-containing liquid which is treated in accordance withthe present invention, can be obtained through the use of conventionalextraction processes from any sugar-bearing agricultural plant such as,for example, sorghum, can, corn, beet, pineapple, or the like. The rawproduct is cleaned, as by washing and trash separation, then cut orchopped into relatively thin slices by sets of rotating knives or thelike. In such processes, as illus trated in the flow diagram, the rawproduct 1 whether chopped fresh, dry shredded or a mixture of these, issubjected to pretreatment utilizing an extractor 2 comprising a crushingsystem or a diffusion system, or a combination of both, from which isobtained a raw sugar juice 3 containing about 10% sugar solids byweight, e.g., approximately 10 Brix.

Accordingly, the term dilute sugar-containing liquid as used herein, isdefined as meaning raw juice containing about 10% sugar solids, i.e.surcrose, levulose (fructose), dextrose (glucose) or mixtures thereof,which have beeen extracted from a sugar-bearing agricultural product. Itis to be understood however, that the concentration of the preferredstarting material in the present process has been selected primarily dueto economic considerations taking into account the type of refiningequipment currently available, and that this invention can be utilizedwith equal efiicacy to produce a purified liquid sugar concentrate fromsugar-containing liquids in which the concentration of sugar solids isgreater or less than In accordance with the present invention asexemplified by the foregoing objects, the dilute sugar-containing liquid3 is first pretreated using conventional clarification and defecationprocess apparatus 2 to remove a substantial portion of theimpuritiescontained therein. Impurities carried over with the sugarjuice coming from the extraction apparatus 2 include soluble inorganicsalts and various organic compounds as well as insoluble compounds andconstituents contained in the raw agricultural product and in theextraneous material not removed in the cleaning step, which impuritiesappear as suspended solids in the dilute aqueous solution of sugar. Thekind and quantity of ash components found in an extracted sugar juicewill vary depending upon the raw product used, the washing method andthe type of extraction apparatus employed. Typically, for example, in aconventional diffusion process the water which is passed through thechopped raw product to dissolve out the sugar is heated to about 180 to200 F. and tends to dissolve out or carry out compounds or constituentscontained in the raw product which are less likely to be removed in acrushing roll system.

Gross de-ashing is accomplished by treating the dilute sugar-containingliquid with, for example, lime and a carbonate-forming compound such ascarbon dioxide, followed by filtration. In some instances wheredesirable, floculating agents such as Separan manufactured by the DowChemical Company can be employed effectively. Alternatively, aphosphating process using phosphoric acid and lime can be substituted inplace of the carbonatation method.

As the final procedure in the clarification and defecation of the crudesugar solution, the thin juice lime-slurry at a pH slightly on thealkaline side is passed at a temperature selected to minimizetemperature change, generally about 180 to 190 F., through a filter 4 toremove all solid products. Advantageously, direct pressure filtrationapparatus of the type disclosed in U.S. Pat. No. 3,310,171, patentedMar. 21, 1967 by Henry Schmidt, Jr., et al. can be employed in thispurification step. In a leaffilter structure of this type the filtercake is removed periodically from the filter leaves, in situ, primarilyby the energy of fluid impingement, which energy creates secondary andharmonic forces because of being opposed by relatively fixed and movableleaf supports acting on the several filter leaves at spaced-apartpoints. By this method the quantity of fluid used for sluicing ismaintained at a practical minimum while elfecting maximum cake removalfunction in an automatically controlled operation. Such apparatus isparticularly useful in the present process where a relatively heavy cakebuild-up occurs. Cake removal is accomplished by using high velocity,high impact type nozzles that are disposed between leaves on a rotatingvariable flow sluice header. Because of the bottom outlet configurationon the leaves themselves, it is a simple matter to blow the heel fromthe vessel and refill the vessel with a leaching liquid so that the cakemay be leached in place if desired. Alternatively, or subsequently, thevirgin or leached cake can be blown dry with air if the discharge of adry cake is desired. In this case, the entire leaf assembly can berolled out and the cake then discharged into an awaiting pan, trough ortruck. Dry discharge is generally accomplished by means of actuation ofa pneumatic vibrator which can also be used when the filter elementsthemselves are to be washed in place. It is a feature of the presentinvention that all defecation products produced in. the process arecascaded to the first filtration station, which is a dry dischargestation, so that all such products are available at about 50%moisturefor simple hauling away with the result that pollution problems aregreatly simplified.

It has also been found that by lowering the extraction temperature inthe dilfusion step to a temperature in the range of about from to F. theamount of ash and color in the juice extracted from the raw product canbe markedly reduced thereby reducing substantially the operating costsof further refining the product. Suitable cold extraction apparatus isdisclosed in copending patent application Ser. No. 718,609 filed Apr. 3,1968.

Following defecation, the pretreated dilute sugar-containing solution ispassed to an evaporator 5 where it is condensed to remove a substantialportion of the water contained therein prior to further purificationtreatment for the removal of the remaining ash components. Preferably,in accordance with this invention, the pretreated solution is evaporatedto produce a sugar liquid 6 having a concentration in the range of fromabout 30 to 60 Brix. Advantageously, the condensation can be carried outusing a multi-efiect steam heated evaporator of the type generallyemployed in conventional sugar refining processes. Thereafter, the sugarliquor from the evaporator of from about 30 to 60 Brix and morepreferably in the range of from about 40 to 45 Brix, is demineralizedbymeans of suitable ionexchange materials in conventional demineralizerequipment 7.

While the impurities which make up the ash components vary with thenature of the raw sugar-bearing agricultural product as well as with theareas in which such products are grown, some of the more common ashcomponents which must be removed are sodium, potassium, calcium ormagnesium salts, silica, traces of iron and certain organic compounds.The cation exchange material exchanges H+ for Na+, K Ca++, Mg++ and thelike, the acid thus formed being retained in the juice and the exchangeion remaining with the cation exchange material. The anion exchangematerial has the opposite chemical property and tends to take up orabsorb the acid, exchanging an OH ion therefore. When the anion exchangematerial exchanges OH- for the acid radical such as Cl, SO and variousorganic radicals, such impurity will have been removed from the juice,since the H+ of the acid combines with the OH of the anion exchangematerial to form water and the acid radical remains with the anionexchange material. In the application of the ionexchange process tosugar factories or mills, it has been customary to use several series ofion-exchangers, each series using a cation exchange bed and an ionexchange bed. Further, generally it has been necessary to provideseveral sets of beds so that one set can be utilized for ionexchangewhile the other sets are being regenerated.

In the ion-exchange system of the present invention, preferably thecondensed sugar liquor is passed through a mixed bed of anion and cationresins wherein the ash components are converted to hydrogen andhydroxide which in turn combine to form water. When the resins becomeexhausted they must be regenerated. The cation resin is regenerated withan acid such as hydrochloric or sulfuric acid and the anion resin isregenerated with a base such as sodium hydroxide or ammonium hydroxide.A suitable ion-exchange system for use in the present invention isdisclosed in co-pending applications Ser. No. 396,840 filed Sept. 16,1964 by Clay W. Riley et al. and S 1=.r. No. 431,131 filed Feb. 8, 1965by James F. Zievers et a Generally, it will be desirable to subject thecondensed sugar liquor 6 to a decoloration treatment using granularcarbon or decolorizing resin to remove the remaining organic material.In accordance with this invention the condensed sugar liquor can bedecolorized before (step 6a) or after (step 7a) demineralization asdesired.

Granular carbon has been used as an adsorbent for color, taste and odorfor many years. Conventional systems generally are of the fixed bed,down-flow type, either in single or multiple column station, with theindividual columns used in parallel or in series depending upon therequirements of the process. Granular activated carbon is particularlywell suited to the present process because it can be regenerated andreused. Most advantageously the granular carbon treatment (step 6a or7a) will be carried out in a single column with counter-current flow ofmaterials. In the present invention the liquid either before or afterdemineralization, preferably will be fed into the columns at the bottomand will be taken off at the top. Periodically the column is pulsed. Apredetermined quantity of exhausted carbon is removed from the bottom ofthe column and a like amount of regenerated carbon is added at the top.The result of such a processing is a more eflicient use of the adsorbingpowers of the carbon, lower total inventory of carbon and the productionof less sweet water than would be produced in a fixed columnarprocessing system. Suitable apparatus for use in this process isdisclosed in co-pending application Ser. No. 384,060 filed July 21, 1964by James F. Zievers now U.S. Pat. No. 3,356,220.

The carbon treated condensed sugar liquor is then passed through asuitable filtration apparatus 6b or 7b, to remove the entrained solidssuspended therein. Generally, it will be desirable to recycle thefiltrate for clarity in accordance with standard decoloration practice.Suitable tubular filter apparatus is disclosed in United States PatentNo. 3,244,286 patented Apr. 5, 1966 entitled Filtration Apparatus by H.Schmidt, Jr. et al.

The demineralized and decolorized sugar liquor having a concentrationpreferably not exceeding 60 Brix is thereafter passed to evaporator '8'and condensed to prm duce a purified liquid sugar concentrate product 9having a concentration of at least 65 and preferably of 65 72 Brix. Theliquid product 9 is then polished in a final filter 10 using powderedactivated carbon to produce final product 12.

The following specific example is given to illustrate the extent of ashremoval that can be accomplished by treating a dilute sugar-containingsolution in accordance with the present invention by the elimination ofcrystallization as an essential step of the purification process.

Sugar juice containing 0.864 lb. of sugar solids per gal. (approximately10 Brix) consisting of approximately 90% sucrose and 10%glucose-fructose mixture, and having an ash component content ofextracted from corn is clarified and defecated by treating it in asuitable mixing chamber. In this example a thin juice lime-slurry isproduced on a continuous basis utilizing calcium hydroxide andphosphoric acid in a single stage mixing chamber through which the sugarjuice is passed. The juice pump discharges into a vertical cylindricalchamber having two spaced impellers axially mounted on and driven by asingle shaft. Inlets are provided adjacent each impeller for thetreating chemicals. The hot juice to be treated enters near the bottomof the mixing chamber, passes upwardly through the chamber where it ismixed with the lime-slurry and phosphoric acid and is discharged nearthe top. A suitable lime-slurry of sweet water containing approximately1 lb. of calcium hydroxide per gal. is pumped into upper portion of themixing chamber where it is mixed thoroughly by the top impeller. Anaqueous solution of H PO having a pH of about 2 is injected through thelower inlet into the chamber and mixed thoroughly by the bottomimpeller. The mixed thin juice lime-slurry is treated as need be withcalcium hydroxide to adjust the pH to the slightly alkaline side, e.g.pH=7.2 and pumped to a surge tank and preparatory to filtering out allsolid products. Suitable apparatus for the clarification and defecationtreatment described herein is disclosed in co-pending application Ser.No. 463,230 filed June 11, 1965 by James F. Zievers now U.S. Pat. No.3,391,789 which describes such apparatus and its method of use inremoving ionic impurities from an aqueous solution in a continuousprocess.

Preferably, the thin juice lime-slurry will be circulated through thepressure filtration apparatus to build up cake on the filter leavesusing as a filter-aid the final filter sluicings recovered during thefiltration of the final liquid product. The defecated dilutesugar-containing solution recovered from the pressure filtrationapparatus will have a concentration of approximately 10% Brix and an ashcontent in the range of from about 4 to 4.5%.

Following defecation, the pretreated sugar solution in this example isevaporated in any suitable manner to produce a sugar liquor having aconcentration of from about 40 to 45 Brix.

The condensed sugar liquor is at this point decolorized using granularactivated carbon in accordance with the method referred to above. Theactivated carbon is supplied through a top opening on a single columnand there after the condensed sugar solution is introduced for filteringupwardly through the carbon which removes the melassigenic constituentsand certain other foreign materials contained therein. A commerciallyavailable activated carbon which is suitable for the present process isDarco granules. The carbon treated condensed sugar liquor is then passedthrough a filtration apparatus of the type referred to above to-removethe entrained solids. The filtrate is then recycled for clarity.

The sugar solution at this point is introduced into an ion exchangedevice wherein the ash components of the sugar solution are passed incontact with ion exchange resins in a mixed resin bed. The cation resincan be a monofunctional sulfonated copolymer of styrene anddivinylbenzene. A suitable cation resin is sold by Rohm & Haas under thetrade name Amberlite IR-l20. It has a specific gravity of about 1.3. Theanion resin can be a styrene type anion exchanger produced from styreneand divinylbenzene containing quaternary ammonium groups. A suitableanion resin is sold by Rohm & Haas under the trade name AmberliteIRA-401$. The specific gravity of such anion resin is generally about1.1. The substantial differences in densities between the two types ofion exchangers permit their ready separation either by means of a liquidhaving a density intermediate thereto, so that one will float and theother will sink or by passing water upwards through a bed of mixedexchangers at such a rate that the quaternary ammonium resin is carriedout of the columns whereas the cation exchange resin is not. Afterdemineralization in the manner described above the effluent leaving thecolumn has a pH of 7.0 and an ash content of less than 1 percent.Thereafter, the demineralized and decolorized sugar liquor is condensedby evaporation to produce a purified liquid sugar concentrate producthaving a concentration of at least 65 Brix and an ash content of lessthan 1 percent. This concentrate is then treated with powdered activatedcarbon to control the development of any thermophylic bacteria andcolloidal suspensions and the final product separated by conventionalfiltration techniques.

What is claimed is:

1. A process for manufacturing a purified uncrystallized liquid sugarconcentrate, consisting of the following sequential steps:

(i) condensing a dilute sugar-containing liquid by evaporation to adjustthe concentration of sugar solids in the resultant condensed sugarliquor to a value in the range of from about 30 to 60 weight percent;

(ii) demineralizing said condensed sugar liquor by pass ing it through amixed-resin bed;

(iii) condensing the demineralized sugar liquor by evaporation until theconcentration of sugar solids is at least 65 weight percent;

(iv) filtering the concentrated liquor; and

(v) separating a liquid sugar product containing at least 65 weightpercent of sugar solids having an ash content of less than 1 percent byweight.

2. The process in accordance with claim 1 wherein the 2,563,006 8/1951Collier 12746.1 process includes as an additional step, decolorizing the2,564,820 8/1951 Smit 12746.1 sugar liquor While it is at aconcentration of from 30 2,578,937 12/1951 Kunin et al. 12746.1 to 60weight percent sugar solids. 2,911,329 11/1959 Blann 12746 ReferencesCited 5 MORRIS o. WOLK, Primary Examiner UNITED STATES PATENTS D. G.CONLIN, Assistant Examiner 1,979,781 11/1934 Van Scherpenberg 12746X2,510,980 6/1950 Jacobs et al 12746.1 2,522,022 9/1950 Durant et al.12746.1 10 12740 55

